LONDON (Reuters) - GlaxoSmithKline could file up to 20 new drugs for regulatory approval before 2020 as it seeks to revitalize a portfolio hit by falling sales of best-selling inhaled lung treatment Advair, the company said on Tuesday.

Seven of them may reach the market before the end of decade, it added.

Britain's biggest drugmaker is trying to boost low investor expectations for its pipeline by hosting its first research and development (R&D) day in more than a decade.

Investors, however, saw little to spark immediate earnings upgrades and the shares ended 1.5 percent lower.

The company highlighted projects in six core areas: HIV and other infections, respiratory medicine, oncology, immuno-inflammation, vaccines and rare diseases.

Chief Executive Andrew Witty said around 80 percent of the medicines and vaccines presented had novel mechanisms of action that could make them first-in-class.

"I am very confident of our ability to deliver very substantial new product sales growth momentum over the next five, 10 and 15 years," Witty said, adding GSK could file 20 more products between 2020 and 2025.

Bernstein analyst Tim Anderson said the heavy focus on earlier-stage assets meant there was a high chance many products would fail.

Investor confidence in GSK's R&D has been shaken by some high-profile drug failures at a time when many rivals have been thriving, adding to pressure on Witty to revive GSK's fortunes.

He declined to comment on a report that Pfizer had approached GSK before entering merger talks with Allergan.


Near-term hopes hinge on new injection Nucala for severe asthma, for which a U.S. approval decision is due by Nov. 4, as well as experimental shingles vaccine Shingrix, sirukumab for rheumatoid arthritis, a long-acting HIV medicine called cabotegravir and daprodustat for anemia.

Only Nucala and Shingrix were included in a GSK forecast in May that new drugs would generate sales of at least 6 billion pounds ($9 billion) by 2020 and Witty said this figure now looked conservative.

Still, the company kept unchanged its forecast that core earnings per share would grow at a mid-to-high single-digit rate at constant currencies over 2016-2020.

Despite having sold its marketed cancer drugs to Novartis, GSK is still investing in oncology and it announced a deal with Merck to test its experimental OX40 cancer drug alongside the U.S. company's Keytruda in solid tumors.

Witty said GSK would continue to pursue new cancer avenues such as next-generation immunotherapies and epigenetic drugs, which can turn off cancer-related genes.

HIV drug cabotegravir will enter final Phase III testing in 2016, along with daprodustat, which boosts red blood cells by mimicking the body's response to high altitude.

Fibrogen, which has deals with AstraZeneca and Astellas, already has a similar anemia product in Phase III.

GSK also announced a collaboration with Regulus Therapeutics in hepatitis C, as well as plans for a pivotal study of novel antibiotic gepotidacin. JP Morgan analysts said these Phase III decisions were largely expected.

GSK's R&D event in New York is one of three high-profile investor days being held by major European pharmaceutical companies this week. Roche will hold a pharma day in London on Nov. 5, while Sanofi is hosting a strategy seminar in Paris on Nov. 6.

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